1. Field of the Invention
The present invention relates to an apparatus for and a method of controlling imaging with defects in a captured image caused by defective photosensitive cells in an imaging device minimized. More specifically, the present invention relates to such an apparatus for and a method of performing appropriate defective-pixel correction so that improved-quality moving and still images are displayed and recorded, for example.
2. Description of the Background Art
Recently, a digital camera that has a solid-state imaging device, such as a CCD (Charge Coupled Device), is prevailing. The digital camera photo-electrically converts a subject image that falls on the array of photosensitive cells. For example, a digital camera, capable of recording still images onto a recording medium, compresses and codes a captured still image, converts the coded data to a predetermined format, and then records the data into a memory card composed, for example, of flash memory. Today, a digital camera can record a still image with an integration of 1,300,000 pixels, at the maximum.
With this type of still camera, it would be convenient if, prior to an actual shooting and recording, frames of image captured by the imaging device are sequentially displayed on the liquid crystal display panel of a viewfinder so as to enable shooting control, such as framing, exposure and focusing control, and auxiliary flashing, to be performed while monitoring the frames of image.
The image signal from the solid state imaging device sometimes inherently contains defective pixels caused by defective photosensitive cells which form pixels but fail to generate the electric charge corresponding to the amount of light incident thereto or in which a noise exceeding a predetermined level is generated due to an uneven dark current. When an image represented by the image signal is displayed, those defective pixels appear as white defects, black defects, or modulation defects in the display image, significantly decreasing the image quality.
To correct these defective pixels, the video camera disclosed in Japanese Patent Laid-Open Publication No. 143404/1995, for example, employs a defective pixel correction method. This method uses low-pass filters for the output produced by previous-pixel-value interpolation or uses only low-pass filters to correct defective pixels according to the relation between the defective pixel level and the threshold.
However, the conventional video camera, intended only for shooting and recording moving images or pictures, does not take account of correction processing for shooting and recording still images. For example, the above-described digital still camera, designed for shooting and recording high-resolution still images, must be able to perform precise pixel defect correction. In this case, still image correction requires a time long enough for correction because there are too many pixels to be processed.
In the movie mode in which the viewfinder function is implemented, it is difficult to spend a period of time in correcting defective pixels in moving images or motion pictures as long as in correcting defective pixels in still images. This is because moving images must be displayed almost in real time to allow processing, such as framing, to be performed. As a result, only intermittent frames would be processed if defective-pixel correction, as performed on still images, must be performed on moving images. This results in more lost frames, preventing moving images from being displayed continuously and making the monitor display unsuitable for deciding framing before shooting. Therefore, although appropriate defective-pixel correction is performed for still images recorded in a memory card, no defect correction is performed during movie mode operation. Defective pixels, which appear on the liquid crystal display panel as defects such as bright or dark dots, degrade the monitor display quality.
The present invention seeks to solve the problems associated with the prior art described above. It is therefore an object of the present invention to provide an apparatus for and a method of controlling imaging in which defective pixels due to defective photosensitive cells in the imaging device can be corrected to output improved-quality still images, even as well as improved-quality moving images for monitoring before shooting and recording.
To solve the above-mentioned problems, the present invention provides an imaging control apparatus for receiving an image signal output from an imaging device which photo-electrically converts an optical image formed by an imaging lens and outputting moving images and a still image represented by the image signal. The imaging control apparatus comprises a signal processor for processing the image signal; a storage circuit for storing therein defect information on defective pixels contained in the imaging device; an output circuit for outputting the image signal, processed by the signal processor to an operation mode; and a control circuit for controlling the imaging device, signal processor, and output circuit to set up the operation mode, the operation mode being one of a moving image mode in which the moving images are output and a still image mode in which the still image is recorded, the control circuit driving components in response to the setup to cause the moving images associated with the image signal to be output and to cause the still image associated with the image signal to be recorded in a recording medium, wherein the control circuit recognizes the defective pixels in the image signal based on the defect information and, based on the recognition result, controls the signal processor, and wherein, under the control of the control circuit, the signal processor calculates, in the still image mode, a value of a position of each of the defective pixels based on the values of the pixels adjacent to the defective pixel, replaces the value of the defective pixel with the calculated result, and outputs the image signal to the output circuit, and, in the moving image mode, replaces each of the defective pixels with the value of a previous pixel and outputs the image signal to the output circuit.
Furthermore, to solve the above problems, the present invention provides an imaging control apparatus for receiving an image signal output from imaging device which photo-electrically converts an optical image formed by an imaging lens and outputting moving images and a still image represented by the image signal. The imaging control apparatus comprises a signal processor for processing the image signal; a storage circuit for storing therein defect information on defective pixels contained in the imaging device; an output circuit for outputting the image signal, processed by the signal processor, according to an operation mode; and a control circuit for controlling the imaging device, signal processor, and output circuit to set up the operation mode, the operation mode being one of a moving image mode in which the moving images are output and a still image mode in which the still image is recorded, the control circuit driving components in response to the setup to cause the moving images associated with the image signal to be output and to cause the still image associated with the image signal to be recorded in a recording medium, wherein the control circuit recognizes the defective pixels in the image signal based on the defect information and, based on the recognition result, controls the signal processor, and wherein, under the control of the control circuit, the signal processor calculates, in the still image mode, a value of a position of each of the defective pixels based on the values of the pixels adjacent to the defective pixel, replaces the value of the defective pixel with the calculated result, and outputs the image signal to the output circuit, and, in the moving image mode, the image signal whose signal processing level at which the image signal is processed is made lower than the signal processing level in the still image mode to reduce an effect of the defective pixel is output to the output circuit.
Furthermore, to solve the above problems, the present invention provides a method of controlling imaging while receiving an image signal output from imaging device which photo-electrically converts an optical image formed by an imaging lens, and outputting moving images and a still image represented by the image signal. The imaging control method comprises the steps of storing defect information on defective pixels contained in the imaging device; processing the image signal; outputting the image signal processed in the step of processing the signal according to an operation mode; and controlling processing in the steps of imaging, processing the signal, and outputting to set up the operation mode, the operation mode being one of a moving image mode in which the moving images are output and a still image mode in which the still image is recorded. In the step of controlling, in response to the setup, the moving images associated with the image signal are output and the still image associated with the image signal is recorded in a recording medium. In the step of controlling, the defective pixels in the image signal are recognized based on the defect information and, based on the recognition result, the step of processing the signal is controlled. In the step of controlling, in the still image mode, a value of a position of each of the defective pixels is calculated based on the values of the pixels adjacent to the defective pixel and the value of the defective pixel is replaced with the calculated result, and, in the moving image mode, each of the defective pixels is replaced with the value of a previous pixel.
Furthermore, to solve the above problems, the present invention provides a method of controlling imaging while receiving an image signal output from imaging device which photo-electrically converts an optical image formed by an imaging lens and for outputting moving images and a still image represented by the image signal. The imaging control method comprises the steps of storing defect information on defective pixels contained in the imaging device; processing the image signal; outputting the image signal processed in the step of processing the signal according to an operation mode; and controlling processing in the steps of imaging, processing the signal, and outputting to set up the operation mode, the operation mode being one of a moving image mode in which the moving images are output and a still image mode in which the still image is recorded. In the step of controlling, components are driven in response to the setup to cause the moving images associated with the image signal to be output and to cause the still image associated with the image signal to be recorded in a recording medium. In the step of controlling, the defective pixels in the image signal are recognized based on the defect information and, based on the recognition result, the processing in the step of processing the signal is controlled. In the step of processing the signal, in the still image mode, a value of a position of each of the defective pixels is calculated based on the values of the pixels adjacent to the defective pixel, the value of the defective pixel is replaced with the calculated result, and the image signal is output, and, in the moving image mode, the image signal whose signal processing level at which the image signal is processed is made lower than the signal processing level in the still image mode to reduce an effect of the defective pixel is output.